New Debian openssl 1.1.0f-3+deb9u2 fixes:
This update addresses the following issues:
* Because of an implementation bug the PA-RISC CRYPTO_memcmp function is
effectively reduced to only comparing the least significant bit of each
byte. This allows an attacker to forge messages that would be considered as
authenticated in an amount of tries lower than that guaranteed by the
security claims of the scheme. The module can only be compiled by the HP-UX
assembler, so that only HP-UX PA-RISC targets are affected. (CVE-2018-0733)
* Constructed ASN.1 types with a recursive definition (such as can be found
in PKCS7) could eventually exceed the stack given malicious input with
excessive recursion. This could result in a Denial Of Service attack. There
are no such structures used within SSL/TLS that come from untrusted sources
so this is considered safe. (CVE-2018-0739)
* There is an overflow bug in the AVX2 Montgomery multiplication procedure
used in exponentiation with 1024-bit moduli. No EC algorithms are affected.
Analysis suggests that attacks against RSA and DSA as a result of this
defect would be very difficult to perform and are not believed likely.
Attacks against DH1024 are considered just feasible, because most of the
work necessary to deduce information about a private key may be performed
offline. The amount of resources required for such an attack would be
significant. However, for an attack on TLS to be meaningful, the server
would have to share the DH1024 private key among multiple clients, which is
no longer an option. (CVE-2017-3738)
CVE-2017-3738 openssl: rsaz_1024_mul_avx2 overflow bug on x86_64
CVE-2018-0733 openssl: Implementation bug in PA-RISC CRYPTO_memcmp function allows attackers to forge authenticated messages in a reduced number of attempts
CVE-2018-0739 openssl: Handling of crafted recursive ASN.1 structures can cause a stack overflow and resulting denial of service